My research interests center on the magneto-electronic properties of semiconductors. The work is focused on the lower-dimensional electron systems formed in synthetically created quantum wells and superlattices. Photonic transitions between quantum levels in the wells, and between magnetic levels induced by strong external magnetic fields, are studied using both a far-infrared, optically-pumped laser system as well as a Fourier transform infrared spectrometer. Our group's goals include the determination of electron dispersion as well as relaxation processes
We are especially interested in novel properties of quantum-well systems caused by band structure effects such as mass-mismatch and extreme non-parabolicity. Our work is made possible by the flexibility for designing quantum-well systems with the MBE system as part of the Center for Semiconductor Physics in Nanostructures (C-SPIN). Our experiments concentrate on the narrow-gap system InSb which, as a quantum well material, shows much promise for infrared and laser devices. We have been able to determine the defining characteristics of the binding potentials for these quantum wells (gap mismatch and band offset). We have observed spin resonance in this system and, in asymmetric wells, evidence of spin splitting in zero magnetic field because of strong spin-orbit coupling. Spin-orbit effects are also responsible for spin-dependent anticrossing behavior which we recently observed in this system.
A recent study of the exciton spectrum in high magnetic fields has led to first results in understanding the holes in InSb quantum wells that subsequemt cyclotron resonance experiments have confirmed.
"Effect of Strain and Confinement on the Effective Mass of Holes in InSb Quantum Wells,"C.K. Gaspe, M. Edirisooriya, T.D. Mishima, P.A.R. Dilhani Jayathilaka, R.E. Doezema, S.Q. Murphy, M.B. Santos, L.C. Tung and Y-J. Wang,Journal of Vacuum Science and Technology B,29, 03C110, (2011)ADS: 2011JVSTB..29cC110G
"Cyclotron resonance in p-doped InSb quantum wells,"M.B. Santos, M. Edirisooriya, T.D. Mishima, C.K. Gaspe, J. Coker, R.E. Doezema, X. Pan, G.D. Sanders, C.J. Stanton, L.C. Tung, and Y-J. Wang,Physics Procedia, (Elsevier, 2010) p. 1201
"Magnetoexcitons in Strained InSb Quantum Wells,"W.Gempel, X. Pan, T. Kasturiarachchi, G.D. Sanders, M. Edirisooriya, T.D. Mishima, R.E. Doezema, C.J. Stanton, and M.B.Santos,Springer Proceedings in Physics, (Springer, 2008) p. 213